Injection molding apparatus having a cooled core

ABSTRACT

Injection molding hot runner apparatus having a cooled mold core with an elongated body portion with a front portion or head. A cooling tube extends centrally in body portion of the mold core. A cooling fluid circuit extends from the open front end of the cooling tube outwardly through a number of spaced radial bores. Each radial bore connects to an L-shaped duct leading back to a cylindrical space around the cooling tube.

This application is a Continuation-in-part of application Ser. No.08/802,048 filed Feb. 8, 1997 now abandoned.

BACKGROUND OF THE INVENTION

This invention relates generally to injection molding and moreparticularly to hot runner apparatus having improved cooling provided bythe circulation of cooling fluid through spaced openings in a frontportion of an elongated core.

The cycle time of hot runner injection molding systems can be reduced byproviding increased cooling to the cavity. Reducing cycle time by even afraction of a second is very important in large volume applications suchas making closures with millions or even billions of moldings. As seenin U.S. Pat. No. 5,094,603 to Gellert which issued Mar. 10, 1992, it iswell known to provide the mold with a cooled core by circulating coolingwater through a central cooling tube in the core. While this issatisfactory for many applications, there is still a considerable delayin the molding cycle before the mold is opened for ejection waiting forthe melt to solidify. As the front portion of the cooled core forms partof the cavity, improved cooling must be achieved without unduly reducingthe structural strength of this front portion of the cooled core.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to at leastpartially overcome the disadvantages of the prior art by providing acooled core with spaced openings in a front portion through whichcooling fluid is circulated to improve cooling to the cavity.

To this end, in one of its aspects, the invention provides an injectionmolding hot runner apparatus having one or more heated nozzles seated ina cooled mold to convey melt to a gate leading to a cavity. The mold hasone or more cooled cores having an elongated body portion, a centralbore, and a front end. The cooled core has a front portion having anouter surface forming one side of the cavity extending around the frontportion of the cooled core. The cooled core has a central cooling tubeextending in its central bore with a first cylindrical space extendingbetween the cooling tube and the surrounding body portion. The centralcooling tube has an open front end inside the front portion of thecooled core, whereby a cooling fluid circuit is provided extendinginside the cooling tube and along the first cylindrical space outsidethe cooling tube to cool the cooled core. The improvement comprises thefront portion of the at least one cooled core having a number of spacedopenings extending outwardly therein through which the cooling fluidcircuit extends. Each opening has an inner end and an outer end. Theinner end of each opening is located adjacent the open front end of thecooling tube to receive cooling fluid therefrom. The outer end of eachopening is connected by rearwardly and inwardly extending cooling fluidflow means to the first cylindrical space extending rearwardly betweenthe cooling tube and the surrounding body portion of the cooled core.

Further objects and advantages of the invention will appears from thefollowing description taken together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a portion of a multi-cavity injectionmolding system showing a cooled core according to one embodiment of theinvention,

FIG. 2 is a larger sectional view of the cooled core seen in FIG. 1,

FIG. 3 is a sectional view taken along line 3—3 in FIG. 2,

FIG. 4 is a partially cut-away isometric view showing the insert inposition for mounting in the body portion of the cooled core,

FIG. 5 is a sectional view of them assembled together for brazing,

FIG. 6 is an isometric view similar to FIG. 4 showing the insert andbody portion of a cooled core according to a second embodiment of theinvention,

FIG. 7 is a similar isometric view of a further embodiment of theinvention,

FIG. 8 is a sectional view of the cooled core according to this furtherembodiment, and

FIG. 9 is a sectional view taken along line 9—9 in FIG. 8.

DETAILED DESCRIPTION OF THE INVENTION

Reference is first made to FIG. 1 which shows a portion of amulti-cavity hot runner injection molding system or apparatus wherein amelt passage 10 branches in a melt distribution manifold 12 to conveyhot melt through each heated nozzle 14 to a gate 16 leading to a cavity18. While the configuration of the mold 20 depends upon the application,in this case the melt distribution manifold 12 which interconnects thenozzles 14 is mounted between the nozzle retainer plate 22 and the backplate 24 by a central locating ring 26 and insulating and resilientspacer members 28. As can be seen, this provides an insulative air space30 between the melt distribution manifold 12 which is heated by anintegral electrical heating element 32 and the surrounding nozzleretainer plate 22 and back plate 24 which are cooled by pumping coolingwater through cooling conduits 34. Each nozzle 14 extends through anopening 36 in the nozzle plate 22 with its rear end 38 abutting againstthe front surface 40 of the melt distribution manifold 12. It is heatedby an electrical heating element 42 which extends around a central bore44 through which the melt passage 10 extends. The nozzle 14 has aforwardly extending flange portion 46 which sits on a circular seat 48in the nozzle retainer plate 22 to locate the nozzle 12 with aninsulative air space 50 between it and the surrounding mold 20. In thiscase, a two-piece nozzle seal 52 is mounted in the front end 54 of eachnozzle 14 leading to the aligned gate 16.

As also seen in FIG. 1, the mold 20 also includes a cavity retainerplate 56 through which holes 58 extend to receive a cavity insert 60aligned with each nozzle 14. As described in U.S. Pat. No. 5,443,381 toGellert which issued Aug. 22, 1995, the cavity insert 60 has a frontsurface 62 which is shaped to form one side of the cavity 18. Cooling isprovided to each cavity insert 60 by cooling water from an inlet 64flowing through tortuous passages 66 to an outlet 68.

The other side of the cavity 18 is formed by the outer surface 70 of thefront portion or head 72 of a cooled core 74 according to the invention.The cooled core 74 has an elongated body portion 76 which in thisembodiment has the front portion or head 72 which is substantiallylarger in diameter than the rest of the cooled core 74. In theconfiguration shown, a thin portion 77 of the cavity 18 extends betweena cavity ring 78 and a stripper ring 80. The cavity ring 78 is held inplace by a core guide 82 which extends around the body portion 76 of thecore 74. The stripper ring 80 is received in an opening 84 in a stripperplate 86.

Referring now to FIGS. 2 and 3, it can be seen that the elongated bodyportion 76 of the cooled core 74 has a central bore 88 extending intothe head 72. A cooling tube 90 extends through the central bore 88 inthe elongated body portion 76 to an open front end 92 in the head 72.The front end 92 of the cooling tube 90 is threaded screws into thethreaded portion 94 of the central bore 88 in the front portion or head72. The cooling tube 90 is sufficiently smaller in diameter than centralbore 88 to provide an elongated cylindrical space 98 between the coolingtube 90 and the surrounding body portion 76 of the cooled core 74. Thefront portion or head 72 of the elongated body portion 76 of the cooledcore 74 has a number of outwardly extending radial bores 100 equallyspaced around it. Each radial bore 100 has an outer end 102 and an innerend 104 extending from the central bore 88 adjacent the open front end92 of the cooling tube 90. In the embodiment shown, the head 72 haseight embodiments. The head 72 of the cooled core 74 also has an equalnumber of forwardly extending L-shaped ducts 106, each having a rear end108 and an inner end 110. The rear end 108 of each L-shaped duct 106connects with the outer end 102 of one of the radial bores 100 and theinner end 110 of each L-shaped duct 106 connects with the cylindricalspace 98 between the cooling tube 90 and the surrounding body portion 76of the cooled core 74. Thus, as shown by the arrows in FIG. 2, the core74 has a circuit 112 for a suitable cooling fluid such as water flowingthrough the cooling tube 90, radially outward through the radial bores100, along the head 72 and back in through the L-shaped ducts 106, andalong the cylindrical space 98 around the cooling tube 90. Of course, inother embodiments, the direction of flow through the circuit can be theopposite.

Reference is now made to FIGS. 4 and 5 in describing how the cooled core74 according to the invention is made. Firstly, an insert 114 and theelongated body portion 76 are machined of a suitable material such asH13 tool steel. In other embodiments, the insert 114 can be made of amore thermally conductive material such as beryllium copper alloy tofurther improve cooling. As can be seen, in this embodiment the insert114 is made with an upwardly extending stem portion 118 and acylindrical portion 120 extending forwardly from a larger diametercircular flange portion 122. The cylindrical portion 120 has the radialbores 100 extending outwardly adjacent the threaded portion 94 of thecentral bore 88 in the head 72 which receives the open end 92 of thecooling tube 90. The body portion 76 is made with the central bore 88extending to a first seat 124 which extends outwardly and upwardly to alarger diameter second seat 126. L-shaped grooves 128 are machined inthe first seat 124 to form the L-shaped ducts 106 when the insert 114and body portion 76 are assembled together. The first seat 124 is madeto fit around the cylindrical portion 120 of the insert 114. Similarly,the second seat 126 is made to fit around the flange portion 122 of theinsert 114. The body portion 76 is mounted in an upright position andthe insert 114 is lowered into the position shown in FIG. 4 with thecylindrical portion 120 resting on the first seat 124 and the circularflange portion 122 resting on the second seat 126. The body portion 76has a pin 132 extending upwardly from the first seat 124 which fits in amatching hole 134 in the cylindrical portion 120 of the insert 114 toensure that the radial bores 100 in the insert 114 are aligned with theL-shaped grooves 128 in the body portion 76. A quantity of a suitablematerial such as powdered nickel alloy 130 is poured around the flangeportion 122 of the insert 114 which has a bevelled rear surface 136 todirect the powder 130 into place. The insert and body portion 76 arethen loaded into a vacuum furnace and gradually heated to a temperatureof approximately 1925° F. which is above the melting temperature of thenickel alloy. As the furnace is heated, it is evacuated to a relativelyhigh vacuum to remove substantially all of the oxygen and then partiallybackfilled with an inert gas such as argon or nitrogen. When the meltingpoint of the nickel alloy is reached, the nickel alloy 130 melts andflows downwardly around the flange portion 122 and between thecontacting surfaces of the insert 114 and the body portion 76. Thenickel alloy 130 spreads between them by capillary action to integrallybraze the insert 114 and body portion 76 together to form an integralcore 74. The cooled core 74 has a center 131 which is used to machinegrind threads on the outer surface 70 of the head 72 of the cooled core74. The cooled core 74 is then machined to remove the stem portion 118and to reduce the distance of the outer surface 70 of the head 72 isfrom the cooling fluid circuit 112 and the cooling tube 90 is screwedinto place in the central bore 88 of the core 74. While thisconfiguration with the L-shaped grooves 128 being machined in the bodyportion 76 provides an optimum combination of structural strength andcooling provided by the proximity of the cooling fluid circuit 112 tothe outer surfaces 70 of the head 72, in an alternate embodiment, theL-shaped ducts 106 can be made by machining L-shaped grooves in theinsert 114 rather than in the body portion 76. In the embodiment shown,as seen in FIG. 2, the cooled core 74 is only one part 138 which isjoined to another overlapping conventional part 140 to form an elongatedcooled core 74. In this case, the one part 138 is made by themanufacturer and shipped to the mold maker to be brazed or welded to theother part 140. Of course, in another embodiment, the entire cooled corecan be made by one party without requiring two parts.

In use, after the system has been assembled as shown in FIG. 1,electrical power is applied to the heating elements 32, 42 to heat themanifold 12 and the nozzles 14 to a predetermined operating temperature.Cooling water is also circulated by pumps (not shown) through thecooling conduits 34, the cooling passages 66 in the cavity inserts 60,and the cooling fluid circuits 112 in the mold cores 74 to cool the mold20. Pressurized melt from a molding machine (not shown) is thenintroduced according to a predetermined cycle into the central inlet 142of the melt passage 10 of the manifold 12, from where it flows throughthe melt bore 44 of each nozzle 14 to fill the cavities 18. After thecavities 18 are full, injection pressure is held momentarily to pack andthen released. After a short cooling period, the mold 20 is opened toeject the product. After ejection, the mold 20 is closed the injectionpressure is reapplied to refill the cavities 18. This cycle is repeatedin a continuous cycle with a frequency dependent on the size and shapeof the cavities 18 and the type of material being molded. Providing theradial bores 100 for the cooling fluid to flow out into the head 72 ofthe mold core 74 improves cooling and reduces injection cycle time bythe close proximity of the cooling circuit 112 to the cavity 18.Providing the L-shaped ducts 106 allows maximum surface contact betweenthe insert 114 and body portion 76 and gives the integral mold core 74the necessary structural strength to withstand injection pressures. Thecombination of the radial bores 100 and L-shaped ducts 106 ensuresturbulent flow of the cooling water through the circuit 112 whichfurther improves cooling efficiency.

Reference is now made to FIG. 6 to describe another embodiment of theinvention. This embodiment is the same as that described above exceptthat the radial bores 100 extend out to a single L-shaped space 144extending continuously around between the cylindrical portion 120 of theinsert 114 and the first seat 124 of the body portion 76. While thisembodiment of the cooled core does not have as much structural strengthas the embodiment described above, it is sufficient for someapplications.

Reference is now made to FIGS. 7-9 to describe a further embodiment ofthe invention. In this embodiment, the shape of the elongated bodyportion 76 is somewhat different, but it has the first and second seats124, 126 extending from the central bore 88 similar to those shown inFIG. 6. The portion 144 of the elongated body portion 76 forming thefirst seat 124 has a generally cylindrical outer surface 148 extendingfrom the flange portion 122 to a generally flat front end 150. Thecylindrical outer surface 148 of the insert 114 fits within thecylindrical inner wall 146 of the elongated body portion 76. The insert114 again has a number of spaced bores 100 extending radiallytherethrough from the outer cylindrical surface 148 adjacent thethreaded portion 94 of the central bore 88. In this embodiment, theinsert 114 has a number of spaced L-shaped grooves 152 extending in thegenerally cylindrical outer surface 148 and generally flat front end150. The rear end 154 of each L-shaped groove 152 connects with theouter end 150 of one of the radial bores 100 and the inner end 156 ofeach L-shaped groove 152 connects with the cylindrical space 98 betweenthe cooling tube 90 and the surrounding elongated body portion 76 of thecooled core 74. Thus, as shown by the arrows in FIG. 8, the cooled core74 has a circuit 112 for a suitable cooling fluid such as water flowingthrough the cooling tube 90, radially outward through the radial bores100, back through the L-shaped grooves 152, and along the cylindricalspace 98 around the cooling tube 90. Of course, in other embodiments,the direction of flow through the circuit can be reversed. In additionto providing improved cooling by turbulent flow and increased structuralstrength, the L-shaped grooves 152 being entirely in the insert 114provides the advantage that the insert 114 does not have to beaccurately oriented when mounted in the body portion 76.

While the description of the cooled mold core 74 with the cooling fluidcircuit 112 extending outwardly in its front portion of head 72 has beengiven with respect to preferred embodiments, it will be evident thatvarious other modifications are possible without departing from thescope of the invention as understood by those skilled in the art and asprovided in the following claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed is defined as follows:
 1. In an injection moldinghot runner apparatus having at least one heated nozzle seated in acooled mold to convey melt to a gate leading to a cavity, and at leastone cooled core having an elongated body portion, a central bore, and afront end to provide the at least one cooled core with a front portionhaving an outer surface forming one side of at least a portion of thecavity extending around the front portion of the cooled core, the cooledcore having a central cooling tube extending in the central bore of thecooled core with a first cylindrical space extending between the coolingtube and the surrounding body portion of the cooled core, the centralcooling tube having an open front end inside the front portion of thecooled core, whereby a cooling fluid circuit is provided extendinginside the cooling tube and along the first cylindrical space outsidethe cooling tube to cool the cooled core, the improvement wherein: thefront portion of the at least one cooled core has a plurality of spacedopenings extending outwardly therein through which the cooling fluidcircuit extends, each opening having an inner end and an outer end, theinner end of each opening being located adjacent the open front end ofthe cooling tube to receive cooling fluid therefrom, the outer end ofeach opening being connected by rearwardly and inwardly extendingcooling fluid flow means to the first cylindrical space extendingrearwardly between the cooling tube and the surrounding body portion ofthe cooled core.
 2. Injection molding apparatus as claimed in claim 1wherein the outwardly extending spaced openings are radially extendingbores.
 3. Injection molding apparatus as claimed in claim 2 wherein therearwardly and inwardly extending cooling fluid flow means comprises aplurality of spaced L-shaped ducts, each L-shaped duct having a rear endand an inner end, the rear end being connected to the outer end of oneof the radially extending bores, the inner end being connected to thefirst cylindrical space extending rearwardly between the cooling tubeand the surrounding body portion of the cooled core.
 4. Injectionmolding apparatus as claimed in claim 3 wherein the front portion of theat least one cooled core comprises a head which is substantially largerin diameter than the rest of the cooled core.
 5. Injection moldingapparatus as claimed in claim 4 wherein the rearwardly and inwardlyextending cooling fluid flow means comprises a second cylindrical spaceextending rearwardly to a rear end from the outer ends of the radiallyextending bores and a radially extending space extending inwardly fromthe rear end of the second cylindrical space to the first cylindricalspace extending rearwardly between the cooling tube and the surroundingbody portion of the cooled core.
 6. Injection molding apparatus asclaimed in claim 1 wherein the at least one cooled core comprises aninsert integrally seated in the elongated body portion to form the frontend of the cooled core, the insert having the plurality of spacedopenings extending outwardly therethrough.
 7. Injection moldingapparatus as claimed in claim 6 wherein the outwardly extending spacedopenings are radially extending bores.
 8. Injection molding apparatus asclaimed in claim 7 wherein the insert has a generally flat front end anda generally cylindrical outer surface fitting into a portion of theelongated body portion having a cylindrical inner wall, and therearwardly and inwardly extending cooling fluid flow means comprises aplurality of spaced L-shaped grooves in the cylindrical outer surfaceand flat front end of the insert, each L-shaped groove having a rear endand an inner end, the rear end being connected to the outer end of oneof the radially extending bores, the inner end being connected to thefirst cylindrical space extending rearwardly between the cooling tubeand the surrounding body portion of the cooled core.
 9. Injectionmolding apparatus as claimed in claim 8 wherein the front portion of theat least one cooled core comprises a head which is substantially largerin diameter than the rest of the cooled core.
 10. An injection moldingapparatus, comprising: a melt passage for conveying hot melt; a moldincluding a nozzle retainer plate and a cavity retainer plate; and acooled core, wherein the nozzle retainer plate is provided with a heatednozzle in communication with the melt passage, the cavity retainer plateis provided with a cavity insert for forming one side of a cavity, andthe cooled core is provided with a head with an outer surface forforming the other side of the cavity, whereby hot melt is conveyedthrough the melt passage, through the heated nozzle, through a gate, andinto the cavity, and wherein the cooled core is provided with a coolingtube having one end extending into the head, and the head is providedwith a plurality of spaced openings extending from the one end of thecooling tube, whereby a cooling fluid is circulated through the coolingtube and the spaced openings in order to cool the head of the cooledcore.
 11. An injection molding apparatus in accordance with claim 10,wherein the cooled core comprises an elongated body portion and aninsert, the elongated body portion having a central bore through whichthe cooling tube extends, the central bore extending outwardly at thehead to a larger diameter seat to fit around the insert.
 12. Aninjection molding apparatus in accordance with claim 10, wherein thehead is substantially larger in diameter than the rest of the cooledcore in order to provide increased cooling to the cavity.
 13. Aninjection molding apparatus in accordance with claim 11, wherein thespaced openings are outwardly extending radial bores.
 14. An injectionmolding apparatus in accordance with claim 13, wherein the radial borescommunicate with L-shaped ducts formed when the insert and the elongatedbody portion are assembled together.
 15. An injection molding apparatusin accordance with claim 11, wherein the elongated body portion and theinsert are brazed together to form an integral cooled core.
 16. Aninjection molding apparatus in accordance with claim 11, wherein thecooling tube is sufficiently smaller in diameter than the central boreto provide an elongated cylindrical space between the cooling tube andthe elongated body portion, and wherein the spaced openings communicatecooling fluid through the head and between the cooling tube and theelongated cylindrical space.
 17. A cooled core for cooling a moldcavity, comprising: an elongated body portion with a head having anouter surface for forming one side of the mold cavity; and a coolingtube having one end extending into the head, the head being providedwith a plurality of spaced openings extending from the one end of thecooling tube, whereby a cooling fluid is circulated through the coolingtube and the spaced openings in order to cool the head of the cooledcore.
 18. A cooled core in accordance with claim 17, wherein the head issubstantially larger in diameter than the rest of the cooled core inorder to provide increased cooling for the mold cavity.
 19. A cooledcore in accordance with claim 17, wherein the cooled core comprises anelongated body portion and an insert, the elongated body portion havinga central bore through which the cooling tube extends, the central boreextending outwardly at the head to a larger diameter seat to fit aroundthe insert.
 20. A cooled core in accordance with claim 19, wherein thespaced openings are outwardly extending radial bores.
 21. A cooled corein accordance with claim 20, wherein the radial bores communicate withL-shaped ducts formed when the insert and the elongated body portion areassembled together.
 22. A cooled core in accordance with claim 19,wherein the cooling tube is sufficiently smaller in diameter than thecentral bore to provide an elongated cylindrical space between thecooling tube and the elongated body portion, and wherein the coolingfluid flows through the cooling tube, outward along the head, back in,and along the cylindrical space around the cooling tube.